1. Field of the Invention
This invention relates to a semiconductor element structure which is usable as an electron beam source such as an electron emitter or in fabrication processes of semiconductor devices. This invention also relates to an electron emitter including the semiconductor element structure.
2. Description of the Related Art
An electron beam is employed in a measuring instrument such as an X-ray generating apparatus and a semiconductor micro-processing apparatus such as an electron beam exposing apparatus. In addition, the electron beam is employed as a beam source for exciting a fluorescent material. Conventionally, the electron beam has been made from a high melting point metallic material such as W or Mo or a compound thereof. Electron emission from the high melting point material is based on the principle of thermo-ionic emission, so that it is required to heat and maintain the material at a higher temperature. In view of energy saving, however, it has been desired to improve the conventional use of the high melting point material.
With the development of information technology, on the other hand, demand for a flat panel display as a display device of character/image information is increased, so that liquid display devices and plasma display devices have been developed. In case of a cold cathode flat panel display, the function is obtained by means of electron beam excitation which is also employed for a CRT. Since the cold cathode flat panel display can reduce the electric power consumption, and, is thinned and downsized, the practical use is desired. As of now, however, since the cold cathode material and the fabricating technique can not be established, the cold cathode flat panel display is not available commercially.
It is required to make the cold cathode electron beam source from a low electron affinity material such as diamond. As for the diamond, the electron affinity is very low, but the productivity may be deteriorated due to the poor processing performance. In case of Si, the productivity can be enhanced due to the excellent processing performance to reduce the driving, but the lifetime is deteriorated due to the high electron affinity.
Recently, using a carbon nanotube, a sharp emitter tip is obtained, so that the driving voltage can be reduced substantially and the brightness can be enhanced. As of now, however, the fabricating process can not be established.
In the above-mentioned respect, it has been desired to develop a new material for establishing a long life-time and high brightness electron beam source.